1. Field of the Invention
The present invention relates to movable body apparatuses, exposure apparatuses, exposure methods, and device manufacturing methods, and more particularly to a movable body apparatus including a movable body which is movable along a two-dimensional plane, an exposure apparatus including the movable body apparatus, an exposure method using the movable body apparatus, and a device manufacturing method which uses the exposure apparatus or the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner)) are mainly used.
In these types of exposure apparatuses, the position of a wafer stage which moves two-dimensionally, holding a substrate (hereinafter generally referred to as a wafer) such as a wafer or a glass plate on which a pattern is transferred and formed, was measured using a laser interferometer in general. However, requirements for a wafer stage position control performance with higher precision are increasing due to finer patterns that accompany higher integration of semiconductor devices recently, and as a consequence, short-term variation of measurement values due to temperature fluctuation and/or the influence of temperature gradient of the atmosphere on the beam path of the laser interferometer can no longer be ignored.
To improve such an inconvenience, various proposals of inventions related to an exposure apparatus that has employed an encoder having a measurement resolution of the same level or better than a laser interferometer as the position measuring device of the wafer stage have been made (refer to, e.g., PCT International Publication No. 2007/097379). However, in the liquid immersion exposure apparatus disclosed in PCT International Publication No. 2007/097379 (the corresponding U.S. Patent Application Publication. No. 2008/0088843) and the like, there still were points that should have been improved, such as a threat of the wafer stage (a grating installed on the wafer stage upper surface) being deformed when influenced by heat of vaporization and the like when the liquid evaporates.
To improve such an inconvenience, for example, in PCT International Publication No. 2008/038752 (the corresponding U.S. Patent Application Publication No. 2008/0094594), as a fifth embodiment, an exposure apparatus is disclosed which is equipped with an encoder system that has a grating arranged on the upper surface of a wafer stage configured by a light transmitting member and measures the displacement of the wafer stage related to the periodic direction of the grating by making a measurement beam from an encoder main body placed below the wafer stage enter the wafer stage and be irradiated on the grating, and by receiving a diffraction light which occurs in the grating. In this apparatus, because the grating is covered with a cover glass, the grating is immune to the heat of vaporization, which makes it possible to measure the position of the wafer stage with high precision.
However, the placement of the encoder main body adopted in the exposure apparatus related to the fifth embodiment of PCT International Publication No. 2008/038752 was difficult to adopt in the case of measuring positional information of the fine movement stage using a stage device that is a combination of a coarse movement stage that moves on a surface plate and a fine movement stage that holds a wafer and relatively moves on the coarse movement stage with respect to the coarse movement stage, or a stage device of a so-called coarse/fine movement structure, because the coarse movement stage came between the fine movement stage and the surface plate.
Further, substrates such as a wafer, a glass plate or the like subject to exposure which are used in exposure apparatuses such as the scanner are gradually (for example, in the case of a wafer, in every ten years) becoming larger. Although a 300-mm wafer which has a diameter of 300 mm is currently the mainstream, the coming of age of a 450 mm wafer which has a diameter of 450 mm looms near. When the transition to 450 mm wafers occurs, the number of dies (chips) output from a single wafer becomes double or more the number of chips from the current 300 mm wafer, which contributes to reducing the cost. In addition, it is expected that through efficient use of energy, water, and other resources, cost of all resource use will be reduced.
However, with the wafer size increasing, the size and the weight of the wafer stage which moves holding the wafer will also increase. Increasing weight of the wafer stage can easily degrade the position control performance of the wafer stage, especially in the case of a scanner which performs exposure (transfer of a reticle pattern) during a synchronous movement of a reticle stage and a wafer stage as is disclosed in, for example, U.S. Pat. No. 5,646,413, whereas, increasing size of the wafer stage will increase the footprint of the apparatus. Therefore, it is desirable to make the size and the weight of a movable member which moves holding a wafer be thin and light. However, because the thickness of the wafer does not increase in proportion to the size of the wafer, intensity of the 450 mm wafer is much weaker when compared to the 300 mm wafer, therefore, in the case of making the movable member thin, there was a concern of the movable member deforming by the weight of the wafer and the movable member itself, and as a consequence, the wafer held by the movable member could also be deformed, which would degrade the transfer accuracy of the pattern to the wafer.
Accordingly, appearance of a new system that can deal with the 450 mm wafer is expected.